The increased use of explosives by terrorists is posing serious problems to law enforcement agencies, security personnel and airport authorities. Sending of explosive devices even as letter bombs, package bombs, or luggage bombs through the mail and the use of explosive devices against both the civilian and military population has increased throughout the world.
It is known that small quantities of explosives are transferred to the hands during contact with commercial explosives or alternatively may be deposited on the outer surface of letter bombs and packages during the preparation of the explosive device. Furthermore, small quantities of explosives may also be deposited upon the surfaces of tables, benches or other supporting structures used in constructing bombs or other explosive devices. Most explosives used in the preparation of such a device have sufficient vapor pressure at ambient conditions to diffuse traces of those explosives to the surface. The detection of explosives in airport terminals, government buildings, embassies, aircraft, and vehicles requires simple portable and economical devices that can give a quick and positive identification of the presence of traces of explosives residue.
As a result of interest in this area, numerous methods and devices have been developed to reduce the risk to the general population by detecting the presence of said materials and preventing their use. The techniques previously employed include X-ray detection and nuclear techniques such as thermal neutron analysis and nuclear resonance absorption. These techniques have been found to be applicable in the sensing of concealed energetic materials found in luggage or other containers. However, it is extremely difficult to detect the presence of dangerous chemicals such as explosives when carried by a person. Due to the health risks and exposing a human to X-rays and nuclear techniques, authorities are unable to monitor people in the same fashion or as thoroughly as they can luggage or other containers.
As a result, other prior art methods do exist which serve the purpose of detecting the presence of the target compounds vapors in the atmosphere. Among the prior art vapor sensing techniques employed are gross chromatography/chemiluminescence, quadrupole mass spectrometry, ion mobility spectrometry, and animals such as sniffing dogs.
Although these techniques appear attractive, since they are capable of atmospheric vapor analysis their applications are limited. For instance, when one employs the sensing method of gas, chromatography/chemiluminescence, the response time before the results are obtained is lengthy while quadrupole mass spectrometry is limited in that it suffers from non-selective ionization, that is, all the species entering the ionization region are ionized and transmitted into the mass spectrometer. The additional technique of ion mobility spectrometry is extremely sensitive and has a relative short response time. However, this method is not quantitatively as accurate as the others since the signal dependence on concentration is non-linear. Moreover clustering of the target molecules with water and low mass spectroscopic resolution are problems frequently encountered.
In addition, the use of laser technology has been employed for the detection of trace atmospheric nitro compounds. A sample of the atmosphere containing the suspected compounds is subjected to a laser which operates at or near 226 nm. to photodissociate the target module into NO.sub.2 and its companion radical and thereafter the detection of the characteristic fragment NO by resonance-enhanced multi-photon ionization and/or laser-induced-fluorescence. Although this technique also appears attractive, it requires the utilization of equipment capable of utilizing a pulsed nozzle to accomplish the desired gas through put entering the analysis chamber and thus requires expensive and difficult to operate equipment.
An additional explosive detection kit and method for detecting trace explosives utilizes the technique of providing a sample from a suspect source and then contacting the sample with a plurality of reagents one after the other for the purpose of generating a distinct coloration associated with explosive materials. This process is more suitable for operation by non-skilled personnel such as guards, police officers, and soldiers in airports, boarder crossings, bus station and buses for a simple and quick detection of explosives.
As the use of explosives by terrorists become an ever growing problem worldwide, it is widely recognized that there is a need for and it would be highly advantageous to have a method and device which can be accurately operated by non-skilled personnel with a device that will provide a highly sensitive detection of trace explosives.